Optical whitener



United States OPTICAL WHITENER No Drawing. Application'March 3t), 1956Serial No. 574,999

3 Claims. (Cl. 260329.3)

The invention here presented is a new whitener in 5 the form of dyetypes of substances which are fluorescent under ultra violet or otherlight to yield a brilliant bluish white fluorescence; the agents being aSeries of 3,7-diaminodibenzothiophenedioxide sulfonic acids;particularly p-substituted amidobenzoyl derivatives.

It is well known that cellulosic materials such as paper, cottontextiles and the like have a slight yellowish hue which, particularly inthe case of textile materials, is apt to become more pronounced when thematerial is sub jected to repeated launderings and use. Accordingly, ithas long been the practice to treat many white cotton textiles, whenthey are washed, with a bluing substance, such as ultramarine. It hasbeen found that the slight blue coloration thus imparted to the materialcompensates for the yellowish tint or similar oft-white shade of thematerial so that it appears whiter; such bluing operations, however,result in the absorption of a measurable portion of the total visiblelight falling upon the treated material and, accordingly, the treatedmaterial has a slightly dull appearance.

It has recently been proposed to treat paper or cotton textiles andsimilar cellulosic materials with agents which,

of the spectrum so that in daylight or other light, which includes ultraviolet radiation, the fluorescence of the treating agent compensates forthe slight yellowish tint or similar ofl-white shade, the blue beingcomplementary to yellow. Such fluorescent agents only absorb a negligi-5 ble portion of the visible light falling on the material and,accordingly, as a result of the fluorescence the treated material ismuch brighter as well as whiter in appearance.

While a wide variety of fluorescent agents have been suggested fortreatment of fibrous materials, it has been found that for the treatmentof cellulosic materials, either paper or textiles, the use offluorescent agents which are substantive to cellulose is preferablesince by the use of substantive fluorescent agents a whitening orbrightening eifect which is resistant to laundering is obtained.

Such substantive fluorescent agents have been applied to the material tobe treated therewith either in a separate treating operation, oradvantageously a small amount of the fluorescent agent may beincorporated in the soap or other detergent used for washing thetextiles, and when the textile is washed with a detergent containing afluorescent brightening agent, a small amount is picked up by thematerial so that after drying the material ap- 7O pears much whiter andbrighter than untreated materials.

These fluorescent brightening agents are also useful atetit in treatingtextile materials which are to be, or have been dyed or printed withdischarge paste. The whites of the materials so printed with pastescontaining brightening agents are much whiter than is otherwise thecase.

While numerous fluorescent bleaching or brightening agents haveheretofore been suggested, including diaminostilbene sulfonic andcarboxylic acids and certain acylated derivatives thereof, only a few ofthem have been satisfactory, particularly for use by incorporation insoap or other detergents. In order to be satisfactory for use as abrightening agent to be incorporated with soap or similar detergents,the fluorescent material which is employed should be itself colorless,or nearly so, and must not stain the material. It is necessary that ithave a true bluish fluorescence with no tendency toward impartingvisible yellow tints to the treated fabric. It must also have a properdegree of substantivity towards the ma terials as too small a degree ofsubstantivity renders it valueless as it would be removed in any rinsewaters, and too high a degree of substantivity results in a gradualbuild-up of fluorescent agent on material during repeated launderingsresulting in oft-color shades. The fluorescent agent must be stable tolight and not discolor on exposure. It must also be stable tohypo-chlorite treatment and not discolor under such treatment, and, inaddition, it must fluoresce over a fairly wide pH differential,including both alkali and acid.

The present invention presents a series of compounds which have some ofthe characteristics of dyestuffs or pigments, which in addition show astrong bluish white fluorescence of outstanding brilliance, whichcompounds in addition are readily incorporated into a wide range offabrics, fibers, felted'materials and paper, to yield an 5 outstandingwhiteness in the material to which they are applied. This material is aseries of p-substituted amidobenzoyl derivatives which are bestdescribed as 3,7-diaminodibenzothiophenedioxide sulfonic acids. Broadlythe compound has the following molecular structure:

' where R may be lower alkyl, lower alkoxy, amino or lower mono ordialkylamino, y may be hydrogen or SO 1 group; and z may be hydrogen,alkali metal ion or alkaline earth metal ion.

These compounds are readily prepared, for example, by condensing onemolecular proportion of 3,7-bis(paminobenzoylamino) dibenzothiophenedioxide-2,8-disultonic acid with an excess of more than two molecularproportions of the appropriate amidating agent.

Examples of amidating agents are acetyl chloride, acetic anhydride,ethylchlorocarbonate (ethylchloroformate),

ably improved. vThe white background of photographic prints anddiazotype prints can be improved by incorpo-- rating some of thematerial into the coating formula- Patented Nov. 3, 1959':

3 4 tions. By addition of the substances to discharge pastes, Example Ithe whites obtained upon discharge are decidely whiter than thosedischarges made in the absence of said mate- 5 parts of3,7-bis(aminobenzoyl)dibenzothlophenedirials. If small quantities ofthese materials are added oxide-2,8-disulfonic acid, 79 parts glacialacetic acid and to soaps or other detergents, fibers which are washedusing 5 5 parts anhydrous sodium acetate were heated to reflux theseformulations will be much whiter in the case of and 21.6 parts aceticanhydride was added gradually whites and much brighter in the case ofcolors than during 2 hours. After the acetylation was complete, fabricswhich are washed with ordinary soaps or deterthe reaction mixture waspoured onto 400 parts hot gents. These materials may be used to bleachfabrics. (70-80" C.) water to decompose the excess acetic anhy- In suchcases, the amount of bleach necessary is materially dride. After onehour of stirring the product having reduced and one or more steps in thebleaching operathe following structure was filtered and dried in a vaction, may be eliminated. uum oven at 70 C.

N303S SO3N8 H...OHN- COHN Q NHOC NHOOOH.

7 SO: One of the more important properties of these com- E l H pounds istheir stability in the presence of sodium hypomm? a chlorite bleachmaterials together with their desirable 10 parts of3,7-bis(aminobenzoyl)dibenzothiophencdishade of fluorescence; they areslightly bluer in shade oxide-2,8-disulfonic acid and 98.2 partspyridine were of fluorescence than prior brighteners with the resultheated to 104 for five minutes in order to form the that in daylight thewhiteness of materials to which pyridine salt and then cooled to 10 C.11.4 parts they are applied, is outstandingly enhanced. In additionethylchlorocarbonate were added during one-half hour. they are free fromany trace of green or pink tint in The reaction mixture was added to1500 parts of water fluorescent properties. and the product isolated bythe addition of 150 g. salt.

Thus the product of the invention outstandingly The mixture was stirredfor two hours and the product increases the apparent whiteness of a widerange of was then filtered and dried in the vacuum oven at 75 C.materials by the incorporation thereinto of a dye type The product hasthe following structure:

substance of the triazinostilbene series containing 3,7- When thesubstance of the present invention is applieddiaminodibenzothiophenedioxide sulfonic acid. Other to cotton from awarm soap solution, the cotton mateobjects and details of the inventionwill be apparent from rial shows an outstanding and valuable brighteningand the following description. whitening effect.

The following examples show the preferred. method of When this materialis incorporated into discharge practising the invention, but variousmodifications will pastes and applied to fabrics, the Whites thusobtained be obvious to those skilled in the art. were remarkably whiterthan those obtained using ordi- The first step in the preparation ofthese substances nary discharge pastes. When this material is applied toconsists in the production of necessary intermediates; fibers ofcellulose, wool or nylon, by methods well known as follows: in the art,the white appearance of the fabric is thereby 25.7 parts of3,7-diaminodibenzothiophenedioxide-2,8- much improved. disulfonic acidand 176 parts pyridine were heated to If small amounts of this substanceare added to soap C. and 33 parts 4-nitrobenzoyl chloride was grad- 50or detergent and the resulting mixture is used to wash ually addedduring two hours. 140 parts of av solution fabrics of cellulose, Wool ornylon, the white materials of 20% by volume sodium carbonate was addedand the thus washed are extraordinarily whiter in appearance pyridinewas removed by steam distillation. After all and colored materials arebrighter than similar materials the pyridine was removed, the mixturewas cooled to which are Washed using ordinary soaps or detergents. roomtemperature, filtered and the product dried in a The product and processof the invention thus provide va uum v n at 65 C- material andprocedures for outstandingly increasing the 30 P 0f the3,7-bis(4-niimbeflzoyl) dibEIlZOthiO- white appearance of a wide varietyof surface subphcnedioxide-Z,8-disulfonic acid obtained fromtheprestances. While there are above disclosed but a limited cedingreaction was reduced with hydrogen in. the presnumber of embodiments ofthe process of the invention ence of 5 parts Raney nickel catalystemploying 500 it is possible to provide still other embodiments withoutparts of water as the solvent. The reduction was cardeparting from theinventive concept herein disclosed and ried out at 100 C. for six hours.Upon cooling, most it is therefore desired that only such limitations beimof the Raney nickel catalyst-was removed mechanically posed upon theappended claims as are stated therein with a powerful magnet and the3,7-bis(aminobenzoyl) or required by the prior art.dibenzothiophenedioxide-Z,8-disulfonic acid was filtered Theinventionclairned is: and dried in a vacuum oven at 6570 C. 1. Awhitener having theformula With these two intermediates available, the.new whitwherein R represents a member of the group consisting ener maybe prepared in its various embodiments as of lower alkyl and loweralkoxy and Z represents alkali follows: metal.

. 5 i 6 2. A whitener having the formula Name soma our-c 0-HN-O-C OHNQ-C-NHO DONE-C 0-03, S 03 3. A whitener having the formula References Citedin the file of this patent UNITED STATES PATENTS 2,529,860 Amstutz Nov.14, 1950 2,563,493 Scalera et a1 Aug. 7, 1951 2,573,652 Sealera et a1Oct. 30, 1951 2,616,855 Wheelock Nov. 4, 1952 2,624,710 Thomas Jan. 6,1953 2,635,969 Goldstein Apr. 21, 1953 2,643,197 Savidge et a1 June 23,1953 2,649,385 Kendall et a1. Aug. 18, 1953 2,702,759 Scalera et a1 Feb.22, 1955 2,706,178 Young Apr. 12, 1955 2,719,155 Siegrist Sept. 27, 19552,723,288 Roberts Nov. 8, 1955 2,763,618 Hendrix Sept. 18, 1956 12,765,239 Siegrist Oct. 2, 1956

1. A WHITENER HAVING THE FORMULA